Makes windowserver not send messages during shutdown

services/ui/ws/window_tree_binding.h

Index: services/ui/ws/window_tree_binding.h
diff --git a/services/ui/ws/window_tree_binding.h b/services/ui/ws/window_tree_binding.h
index 34fdf3a0d827ed2c72d190c502fbc73fe0bb50da..4b9b88485e9edec024e3713f9eefd00053eaa277 100644
--- a/services/ui/ws/window_tree_binding.h
+++ b/services/ui/ws/window_tree_binding.h
@@ -33,6 +33,13 @@ class WindowTreeBinding {
 
   virtual void SetIncomingMethodCallProcessingPaused(bool paused) = 0;
 
+  // Called when the WindowServer is destroyed. Sets |client_| to
+  // CreateClientForShutdown().
+  void ResetClientForShutdown();
+
+ protected:
+  virtual mojom::WindowTreeClient* CreateClientForShutdown() = 0;
+
  private:
   mojom::WindowTreeClient* client_;
 
@@ -58,6 +65,10 @@ class DefaultWindowTreeBinding : public WindowTreeBinding {
   mojom::WindowManager* GetWindowManager() override;
   void SetIncomingMethodCallProcessingPaused(bool paused) override;
 
+ protected:
+  // WindowTreeBinding:
+  mojom::WindowTreeClient* CreateClientForShutdown() override;
+
  private:
   mojo::Binding<mojom::WindowTree> binding_;
   mojom::WindowTreeClientPtr client_;